LATEST NEWS

09/17/17
Previous Home pages moved to Real-Time pages; new Home and Introduction pages

09/05/2017
Site design and content partially revised and on-line. More to come.

09/01/2017
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CONTACT ME

jensen@real-time.org

Cell 508-728-0809

http://time-critical-technologies.com

"The first revolution is when you change your mind about how you look at thingsand see that there might be another way to look at itthat you have not been shown."

--Gil Scott-Heron, "The Revolution Will Not Be Televised"

People frequently associate a clock image with real-time computing – in printed documents, on web sites, etc. That is appropriate in the sense that a clock depicts time, and time is the basis for time-constraint driven resource management. But a clock also implies static periodicity – a strong property that underlies traditional static real-time computing concepts and technologies. But the general case of real-time systems is dynamic – task arrivals completions, resource conflicts, etc, The traditional static case is a small subset. Despite inherent uncertainties in dynamic real-time systems, correctness depends on application-specific acceptable satisfaction of timeliness properties. This is analogous to how we adaptively manage the dynamic timeliness of tasks in our personal and professional lives. The distorted clock image on this page is intended to depict the fundamental basis of time while revealing static timeliness as a special case.

Updated on 20 September 2017 at 10:47 pm

Real-Time for the Real World ™

E. Douglas Jensen

This site is about some of my research on real-time (including, but not limited to, computing) systems. (My consulting practice web site is time-critical-technologies.com.)

In particular, it is focused primarily on dynamic—in the sense of dynamically real-time systems (as opposed to other ways that systems can be dynamic).

Common examples of how systems and their applications and their operational environments can result in dynamically real-time properties—i.e., timeliness and predictability of timeliness of their actions—include (but are not limited to):

changes in the system actions’ (e.g., tasks’) expected arrival times and operation (e.g., execution) times, potentially resulting in transient or persistent overloads;

changes in actions’ (e.g., tasks’) completion time constraints, such as deadlines, even during an action’s operation;

changes in actions’ conflicts for access to sequentially shared (hardware and software) resources.

There is an expanse of dynamically real-time systems. Static real-time systems are a special (often important) case end-point on that expanse.

Outside the field of traditional real-time computing, many if not most real-time systems have some degree of dynamically real-time behavior by their actions—i.e., may be anywhere on the dynamically real-time expanse except at its static end-point.

Inside the traditional real-time computing field, most systems are predominantly, if not entirely, very near or at the static end-point of the dynamically real-time expanse.

This site explicitly defines the concepts of real-time per se, and related concepts such as predictability and hard/soft in terms of a mental model in a framework—quality of service—based on first principles about latency. The scholarly approach (and anything similarly rigorous) here can be found nowhere else.

An outdated list of selected papers authored by my research teams and myself, and published in professional society (IEEE, ACM) journals and conferences, is provided, and will be updated. Another source for some of those is my Google Scholar page.

N.B. There still are many pages from the previous (c. 2008-2012) version of this site which I have not yet updated and integrated (or removed).

About Me

E. Douglas Jensen is a well-known pioneer and thought leader in real-time and distributed real-time systems–especially dynamic ones.
His professional accomplishments have been in
Innovative industriaRead more

Introduction

This web site is primarily a—indeed, the only currently extant—scholarly exposition of timeliness and predictability of timeliness in the general case of dynamically real-time systems. That content apRead more